Conventional power module assembly structures use a ceramic substrate as a circuit trace substrate. Various components of the power module are disposed on the ceramic substrate, and external wires are soldered at the edge of the ceramic substrate to electrically connect to an outside circuit. The components on the ceramic substrate will generate a great amount of heat due to energization. In the conventional power module assembly structure, the heat of the component is mainly transmitted to the ceramic substrate, and the heat sink is disposed under the ceramic substrate for heat dissipation. Due to the small traces on the ceramic substrate, the heat cannot be quickly conducted through the small traces and the external wires.
In addition, since the structure of the conventional power module is provided with a heat sink under the ceramic substrate, a thermal grease is required to be disposed therebetween. Even if the thermal conductivity of the ceramic substrate and the heat sink are relatively high, the thermal grease usually has lower thermal conductivity. In this way, the heat generated by the components is transmitted to the ceramic substrate through the thermal grease, and is conducted to the heat sink, causing very large heat resistance of the heat flow path, so that the heat dissipation efficiency cannot be improved. In addition, the conventional power module is required to include a heat sink, so that the cost cannot be effectively reduced.
Therefore, it is an important issue in the industry to provide a power module assembly structure with high heat dissipation efficiency and low cost.